Question: Solve for $x$ and $y$ using substitution. ${-2x+y = -4}$ ${x = -4y+11}$
Answer: Since $x$ has already been solved for, substitute $-4y+11$ for $x$ in the first equation. ${-2}{(-4y+11)}{+ y = -4}$ Simplify and solve for $y$ $8y-22 + y = -4$ $9y-22 = -4$ $9y-22{+22} = -4{+22}$ $9y = 18$ $\dfrac{9y}{{9}} = \dfrac{18}{{9}}$ ${y = 2}$ Now that you know ${y = 2}$ , plug it back into $\thinspace {x = -4y+11}\thinspace$ to find $x$ ${x = -4}{(2)}{ + 11}$ $x = -8 + 11$ ${x = 3}$ You can also plug ${y = 2}$ into $\thinspace {-2x+y = -4}\thinspace$ and get the same answer for $x$ : ${-2x + }{(2)}{= -4}$ ${x = 3}$